What I see them doing is this:
1. Solgaleo - Fire
2. Lunaira (or whatever its actual name turns out to be) - Ghost/Flying
3. Marshadow - Dragon/Poison
#1 is almost too obvious, as legendaries tend to have types that make sense but not everyone might expect them to have, but then again, its not like pure orange with flames sticking ou of it everywhere, so that works.
#2 Of course as with Xerneas and Yveltal, the "winged" one of the two has /Flying slapped on it, with both of them having only one actual main elemental type to represent them. The first guess (even before we saw the design) was that the Moon legendary would have Fairy again, since every moon-associated move is Fairy-type, but since I'm fairly certain that these are VERY connected to the XYZ-mascots, I doubt that Lunaira is Fairy/Flying. And neither would it be Dark/Flying as that would be even more repetitive. Then there is the option of Psychic/Flying, which makes sense due to Psy having a loose association with anything "spacey" or cosmic (remember the Psy-Gym in XY for example). I hope not though, as we have Lugia for that already. And I'm sure someone will say Dragon/Flying coz Noivern had Dragon type as well, but eehhhhh. So I'll stick to the other creepy and darker type left, Ghost.
What bugs me here personally, is that now they have made 2 grim/dark flying legends with crescent/Y-designs in a row. And it makes me want to redesign my own grim airborne crescent darkness legendary fakemon Yumra again -____________- (
http://saiph-charon.deviantart.com/art/170-Yumra-315940554)
#3 We're looking at the white plus either turquoise or purple equivalent of Zygarde here. I'm speculating it's another third monster from the underground, as well as having multiple forms and a Core form, in whatever way that will be made use of for Zygarde. I'd put Poison on this one for several reasons. STILL NO FREAKING POISON LEGENDARY for example. And the fact we've had many darker epic legends already, like Yveltal representing destruction and death, yet they did not make use of the actual "anti-life" type that is Poison... so let's give it to the eclipse doomsday Pokemon at least then for once pls? ^^"